An allegation of serious sexual assault made against MP Julian Knight is being looked into by Essex Police, after the case was referred to them by another force.
The Metropolitan Police confirmed in December that it was carrying out an investigation into the then-Conservative MP, who had the party whip withdrawn after the inquiry was launched.
The force said in March that its investigation was over.
But the case has now been handed over to the neighboring team, which has confirmed they are investigating a single allegation.
Mr Knight has denied any accusations against him throughout.
A statement from Essex Police said: “We have agreed to take on an investigation which has been referred to us from the Metropolitan Police Service. We are investigating an allegation of serious sexual assault.
“Detectives who specialize in cases of this kind will gather evidence and conduct a thorough investigation. The senior investigating officer has extensive experience with the force.”
The force also said the investigation “remains at an early stage”.